For visiting manager Louis van Gaal, a first loss of the campaign was a miserable way to mark his 50th game in charge.

United’s defensive fragility

With both teams protecting unbeaten starts to the season, there was a bristling intensity to the early exchanges.

United had not conceded in their opening three matches, but that record was under threat as Swansea pressed with chances for Gomis and Gylfi Sigurdsson.

Daley Blind, a midfielder currently playing at centre-back, offered little resistance as Gomis skipped past him and his central defensive colleague Chris Smalling before clipping the post with a delicate low shot.

Those fragilities were eventually exposed when Ayew and Gomis took advantage of slack marking and dubious goalkeeping to put Swansea ahead.

Monk’s masterstroke

There may have been a few eyebrows raised when, with his team trailing after 57 minutes, Monk replaced winger Wayne Routledge with midfielder Ki Sung-yueng.

But the switch to a midfield diamond was vindicated after just four minutes as Ashley Williams strode out of defence and freed Sigurdsson, whose precise cross found Ayew for Swansea’s equaliser.

The hosts were ahead four minutes later, as Ayew’s artful through-ball with the outside of his foot found Gomis, whose low finish beyond Romero sent the Liberty Stadium crowd wild and gave Monk the satisfaction of a tactical alteration paying off in style.

Van Gaal’s midfield headache

United’s two changes from the midweek Champions League win at Club Brugge saw Van Gaal recall two of his highest-profile summer signings, Bastian Schweinsteiger and Morgan Schneiderlin.

That pushed fellow central midfielder Ander Herrera into a more advanced role behind striker Wayne Rooney, but United struggled for fluency.

The one positive was another bright display from Mata but, playing in his unfavoured position wide on the right, he was substituted after 70 minutes.

Man of the match: Andre Ayew

The tireless Ghanaian forward was a constant menace, taking his goal well and providing a superb pass for Gomis’s winner.

Bafetimbi Gomis (centre) slots the ball under the body of Sergio Romero to secure Swansea’s comeback win against Manchester United

Gomis wheels away in celebration after scoring Swansea’s second – and match-winning – goal against Manchester United on Sunday

As Luke Shaw (right) shuts his eyes in disappointment, Gomis raises a fist in celebration at the Liberty Stadium in Swansea

France international Gomis celebrated in typical fashion, roaring at the Swansea fans after netting the home side’s second goal